<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="utf-8">
	<title>css 学习</title>
	<link rel="stylesheet" type="text/css" href="css.css">
</head>
<body>

	<div>
		<span>哈哈哈哈哈哈</span>
	</div>
		<span>234</span>

	<div class="wrapper">
		<strong class="box">
			<em>1</em>
			
		</strong>
		<em>2</em>
	</div>





	<br>	
	1.选择器<br>
	<div id="demo1" class="demo3">only</div>
	<div id="demo2">demo2</div>

	<div class="demo3">123</div>

	<span>123</span>
	<div>
		<span>456</span>
	</div>

	<div id="demo4" class="class4">123123123</div>
</body>
</html>